The invention relates to a cable terminator, preferably an outdoor terminator for high voltage.
Various types of terminators are known. Older designs are formed with porcelain insulators and an oil or other chemical filling. Such terminators have the disadvantage that they are not very robust mechanically, and no longer fulfil present-day environmental protection conditions with regard to possible substance leakage. A terminator without oil filling is described in EP 667 665 B1. A special feature of this terminator is a rigid conducting element which is designed to take up the lateral forces. The forces are carried awayfrom the overhead conductor connection via the rigid conducting element, via a base body with a field control and insulating device, to the bearing structure. The weak point of this arrangement is the transition tram the conducting, rigid element to the base body.
An object of the invention is to propose a cable terminator, preferably a high-voltage outdoor terminator, which can be produced at low cost, is mechanically stable and entirely satisfies the mechanical requirements.
A terminator is mounted at one end on a base fitting, preferably for fastening to a cross-arm. Means for fastening the cable are formed on the base fitting and have an electrical duct tube or pin inside the terminator. Situated at a top fitting are means for fastening to the pin. Means for electrically connecting the cable shield to ground potential and means for the field control and insulation at the inhomogeneous potential transitions at the cable end are present.
The insulating body generally bears on its surface an elastomeric material (preferably of silicone rubber) with a ribbed surface (shielding plates). The length and in particular diameter of the insulating body is to be chosen such that the demands for sufficient insulation and avoidance of atmospheric flashovers at full operating voltage are met. This requirement can be fulfilled by covering the surface of the insulating body with a resistive or refractive control coating.
The insulating body is fastened to the base fitting. The further, customary means for electrically connecting the cable shield to ground potential and means for the field control (field control bodies) and insulation at the inhomogeneous potential transitions at the cable end are employed. On the fastening to the base fitting, voids present between the cable end and the field control and insulating elements are closed by mechanical bracing with the base fitting.
The insulating body is filled up with material from the region of the fastening to the base fitting up to the level of the contact elements, and that the filling is reduced towards the top fitting, with the result that an internal cavity is formed.
The three parts consisting of electrical duct with contact elements, insulating body and top fitting are produced separately. The top fitting consists essentially of an electrically conductive end plate and an overhead conductor connection piece, in which a thread may be incorporated for the fastening of a carrying lug. The electrical duct, designed as a tube or as a pin, is preferably fastened inside the end plate in a welding operation (or by another firm mechanical connection). The insulating body, consisting of insulating material, is bonded into the top fitting. The unit, also referred to as assembly unit, is lifted by a crane at a carrying lug into the assembly position and lowered from above over the prepared lower part of the terminator. The dimensions of the parts in the lower region of the assembly unit are designed such that upon assembly they slide in a self-centering manner into the base structure on the base fitting. In the process, the electrical duct also comes into contact with the cable conductor via contact elements.
A cable plug system is preferably employed for the contact receptacle; the latter may be fastened to the cable conductor with screws. The electrical contact to the electrical duct is provided by contact laminations. This plug connection is not designed to take up the forces on the terminator. In the present arrangement, the insulating body is therefore constructed and dimensioned so as to be able to take up all the mechanical forces. The plug relieved of mechanical loads. A typical magnitude of the transverse force to be expected is 5 kN, so that the mechanical design is to be dimensioned for this characteristic quantity.
The insulating body is produced from cast resin or another suitable material. It may be materially strengthened, for example with glass fibers. The insulating body is completely filled up with material from the bottom edge up to the level of the contact elements. A cavity is preferably formed in the interior of the insulating body. The cross-section of the cavity (the space filling) may be linear or be reduced in a curve in the shape of a tunnel towards the top fitting. The form of the cavity allows the weight to be kept low, the wall thickness may not be reduced further than a point where the bending forces can be taken up. In a preferred design, the inner surface of the cavity is lined with a conductive coating.